Geology of the Pilanesberg Ring Dike Complex 28 July 2015

Geology of the Pilanesberg Ring Dike complex 28 July 2015

sustain critical watering holes for the animals. The largest body of water in the park, Mankwe Lake, is visible in the lowlands just east of the center.

Several phases of geologic activity created the landscape over hundreds of millions of years. The process began about 1.3 billion years ago, when primitive organisms like algae were the only lifeforms on Earth and huge volcanic eruptions were common. During this period, magma pooled up near the surface in a large hot spot that bulged with immense pressure. The pressure helped push up a volcanic structure that was several thousand meters tall.

Acquired June 19, 2015. Over time, tubes of magma radiated outward from the main magma chamber beneath the volcano. Eventually this created massive cracks in the Earth's surface around the volcano at regular While big game animals such as lions, leopards, intervals. (In cross section, the magma tubes would elephants, rhinos, and water buffaloes draw most have looked something like the branches of a tree visitors to Pilanesberg National Park, the land extending from a common trunk. From above, the these animals live on is just as compelling. radial cracks gave the surface the appearance of a Pilanesberg is located in one of the world's largest broken window. A good illustration of the magma and best preserved alkaline ring dike complexes—a tubes is available here.) After several violent rare circular feature that emerged from the eruptions sent lava bursting from the volcano, the subterranean plumbing of an ancient volcano. center collapsed on itself, squeezing even more magma out from the network of cracks. The Operational Land Imager (OLI) on Landsat 8 acquired this image of the park in South Africa on As volcanic activity waned, the remaining magma June 19, 2015. Seen from above, the concentric cooled in the cracks as bands of volcanic rock rings of hills and valleys make a near perfect circle, (mainly syenites and foyaites). Geologists call with different rings composed of different types of these structures dikes. The rate of cooling and the igneous rock. The entire structure sits about 100 to composition of the magma affected the type of rock 500 meters (300 to 1,600 feet) above the that formed in each dike. For instance, white foyaite surrounding landscape. The highest has particularly coarse grains and is formed when point—Matlhorwe Peak—rises 1,560 meters (5,118 lava cools slowly. Red syenite forms when magma feet) above sea level. contains plenty of water. In the detail image, outcrops of white and green foyaite and of red Several streams run through the valleys and faults, syenite make up the ridges in the southwestern part though most only flow during the wet season of the park. These rock types are especially (between October and April). When this image was resistant to erosion and weathering, so they were acquired in June 2015, the streams had run dry. left behind as hills and ridges while streams and However, man-made dams trap enough water to glaciers scrapped and scoured away weaker types

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of rock.

Acquired July 7, 2015

More information: "Geomorphological Evolution of the Pilanesberg." Landscapes and Landforms of South Africa. DOI: 10.1007/978-3-319-03560-4_5

Provided by NASA APA citation: Geology of the Pilanesberg Ring Dike complex (2015, July 28) retrieved 28 September 2021 from https://phys.org/news/2015-07-geology-pilanesberg-dike-complex.html

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